1. Field of the Invention
The present invention relates to a television receiver wherein images in a plurality of television systems being different in image size aspect ratios can be displayed.
2. Description of the Prior Art
A television receiver in the prior art has a picture tube with the aspect ratio of 16:9 in order to display images in the high vision television system. The television receiver can display also images in the existing standard television system in general.
On the other hand, in the existing standard television system (such as NTSC system), the image size aspect ratio is 4:3, but since an image in a movie or the like is long sideways, in order that the system is converted and the whole picture plane can be displayed in the existing standard television system, software called letter box in which the upper and lower sides are cut may be used. In the letter box size, the effective image size aspect ratio is made about 16:9, and other portion is constituted as a single color such as black. A television receiver in the prior art may be changed in normal mode where the image size is displayed in normal size and in enlargement mode where the image size is enlarged in vertical and horizontal directions.
When the video signals of the letter box size in the existing standard television system are inputted, the image displayed in normal mode becomes as shown in FIG. 3(a), but the image displayed in enlargement mode becomes as shown in FIG. 3(b) and the effective image state can be obtained. Also when the video signals of normal size in the existing standard television system are inputted, the image displayed in enlargement mode becomes as shown in FIG. 4(b) where the image is lacking in upper and lower sides and a problem of conflict with the copyright may occur and the effective information can not be displayed. Consequently, the display in normal mode as shown in FIG. 4(a) is preferable.
In a television receiver in the prior art, since changing of enlargement mode and normal mode in the picture plane is performed by manual operation, the changing work is troublesome. Particularly, if a commercial message or the like is inserted at the midway of software in letter box size, the changing work is troublesome and the picture plane can not be seen well.